High phosphate in tap water

Discussion in 'Water Chemistry' started by Maximumbob, 13 Jul 2007.

  1. Maximumbob

    Maximumbob Member

    Messages:
    119
    Location:
    Cheshire, UK
    Not sure if this is the correct place to put this post... but it crosses a few boundaries.

    Basically my tap water phosphate is 5-10ppm!!! (HOLY moly I hear you cry)

    I have been trying to dose N,K & trace to see if the plants soak up the phos. But there is too much. I'm suffering from various minor algae outbreaks on a regular basis, and my anubias are covered in green dusty algae.

    In an experiment I introduced API Phoszorb, within 12 hours my tank phosphate was down to 0.5-1ppm. (Its not a true experiment as I introduced Purigen at the same time - whilst the water is clearer, I'm unsure whether it will have an effect on plant growth)

    Since then the plants have noticeably improved, increase photosynthesis etc. I am wondering whether a high phosphate can have an inhibitory effect on some plant growth?

    My next difficulty is finding how long the Phoszorb will last. I don't want to be crippled with the expense of combating high tap phosphate levels.

    Any comments or experience to help me?
     
  2. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    That is a very good question and one I don't know the answer to. Theoretically no it shouldn't but I've noticed some very strange things using EI where I've had an amount of something that has caused a bit of stunting. Lowering the amount has often improved things. It's normally only subtle changes in a particular plant or two. It never seemed to cause any problems with algae though, only plant appearance.

    What can you do? Not a lot without hassle really. I use a blend of RO and tap water to get water parameters the way I like, but then again my tap has GH pf 28

    HTH
    James
     
  3. George Farmer

    George Farmer Founder Staff Member

    Messages:
    7,089
    Location:
    Cambridgeshire
    That's very interesting. My PO4 is 5+ppm yet I'm getting good growth and pearling with just 1wpg T8 in my 125 l.

    My NO3 is 20ppm from the tap too.

    So I wonder if the ratio is important. 4:1 NO3:pO4 is what EI doses I think, so I may be lucky.

    BTW I still add more NP via Tropica+ liquid. Minimal algae.

    It would be interesting to see what effects reducing PO4 would have. I may stick some RowaPhos in there just for fun!
     
  4. fishgeek

    fishgeek Member

    Messages:
    117
    Location:
    west sussex
    i dont know what you guys think of the redfield ration

    basically reverse science in that aquatic (marine i think the intial study was done in) plants all seemed to have PO4 and NO3 at a particular ratio

    so some aquarists have used this ratio in the water to control algal growth

    in the case o f high phosphates it may be neccesary to increase the nitrates with something like KNO3 , rather than reduce phosphates

    andrew
    if interested googe redfield ratio calculator , takes you to a nice summary and a simple calculator for how much of what maybe needed..
     
  5. Maximumbob

    Maximumbob Member

    Messages:
    119
    Location:
    Cheshire, UK
    his is the best thing that I can come up with about the redfield calc that makes sense. he only problem is that I've been muling it over fora few weeks and come to the conclusion that I dont know enough Dutch!!!

    http://www.xs4all.nl/~buddendo/aquarium ... .htm#algen

    Some of the components are in dutch and I dont know what they mean. This coupled with the fact that the ratios dont account for my high tap water phosphate levels. I tend to be told to do a water change!

    Confused still.

    In my study I have a 60 litre tank which I've been dosing with KNO3 and trace twice weekly and keeping CO2 at good levels. Am currently plagued with BGA and what appears to be Oedogonium. This tank hasnt had the phoszorb added... I've pulled out all the contaminated stems and replaced them with new ones hoping they would strip the water column of its nutrients and starve the algae. Unfortunately this hasn't worked :( Next step blackout.

    I just am annoyed that my 180 litre is looking so well and my 60 litre so bad :(
     
  6. neil1973

    neil1973 Newly Registered

    Messages:
    14
    Location:
    Stirling
    I wouldn't worry about the amount of phosphate in your tap water unless you think it is causing specific problems. As long as you do regular water changes it will save you having to add any. I would tend to look at how the plants are doing rather than worrying about specific numbers - test kits tend to be fairly inaccurate. I would also be very wary of using phosphate removers as you may end up removing too much phosphate which wont be good for your plants.

    I don't think the ratio between NO3 and PO4 is very important as long as both are present. The redfield ratio isn't relevant to planted aquariums. It is based on work with marine phytoplankton. Another important consideration is that it is an atomic ratio (relative number of atoms) rather than a mass ratio. This is generally overlooked by people trying to apply it to aquariums meaning they normally have the ratio wrong by a considerable margin.

    cheers
    Neil
     
  7. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Hi Maximumbob,
    Trying to get my head wrapped around this issue. The implication of your experience is that at some level of PO4 plant growth is reduced. It's also implied that the high PO4 level in the tap is a causal factor in the algal outbreaks. Like some of the other posters I have doubts about this for several reasons:

    1. PO4 test kits are notoriously unreliable. The tap readings are immediately suspect though the 5-10 ppm mentioned may have been from your water report.

    2. As a result of this reading it appears you then dosed only N and K + trace and did not provide any inorganic source of P by assuming that there was sufficient P. You then experienced subsequent algae outbreaks and slow growth. You mention that "there was too much [PO4]..." and immediately concluded that the algae outbreaks were a result of the excess PO4.

    Fundamentally I'm having trouble with this conclusion based on my firm belief in the EI method and based on the Barr Report Newsletter - Phosphorous ( http://www.barrreport.com/barr-report-n ... horus.html )
    The Report concludes that PO4 is not a causal factor in algae proliferation.

    Similar to the Nitrogen issue this report discusses the four forms of PO4:

    1. Particulate organic phosphorus = (POP), derived mainly from dead
    plant material and microbial biomass.
    2. Dissolved organic phosphorus = (DOP), organic P in dissolved from that may pass through a 0.45 µm filter.
    3. Particulate inorganic phosphorus = (PIP), Inorganic P associated with minerals such as Fe and Al oxides or calcium carbonate.
    4. Dissolved reactive phosphorus = (DRP), the P that is bio-available. Sometimes referred to as : soluble reactive P (SRP)

    The newsletter goes on to discuss that the organic forms of Phosphorous are assimilated at a much slower rate and that this slow rate could result in Phosphorous limiting unless supplemented by inorganic dosing.

    It is possible therefore that if you did not dose PO4 your algae outbreaks could have been a result of Phosphorous limiting, not of excess Phosphorous.

    Another possibility is that the test kit did accurately reflect the PO4 content, that there was sufficient inorganic content but that a higher PO4 uptake drove a higher Nitrogen uptake and that you were Nitrogen limited. You didn't list your dosing scheme so it's difficult to say. A lowered PO4 availability could conceivably have lowered the drive for Nitrogen uptake.

    You also didn't mention your CO2 dosing so again, it's difficult draw any real conclusions.

    I guess what I'm trying to say in a long winded way is that there are way too many variables in the system to draw easy conclusions for causality. For example you changed two variables at once adding the Poszorb and the Purigen so there are multiple dynamics at work (the Purigen removes organic Nitrogen including NH4, a known cause of algae). You have seen an improvement and that ought to be good enough, but to really test your conclusion you should either remove the Phoszorb only or, now start dosing KH2PO4, in boths cases being mindful of increased Nitrogen demand. This is on the assumption, that like Purigen, the Phoszorb removes the organic PO4.

    It would be really interesting to see the results.

    Cheers,
     
  8. Maximumbob

    Maximumbob Member

    Messages:
    119
    Location:
    Cheshire, UK
    Thsnks for the detailed reply.

    I'll get onto reading the phosphate newsletter asap.

    I do think that the imbalance of nutrients is a problem as you say. I just didnt know how to address it. Its then that I thought by removing phosphate and then dosing the tank I could see how things go.

    It may be just a case of 'cleaning' the tap water and dosing with KH2PO4 again.

    I have DIY CO2 and I regulate changes in mix according to my drop checker (4DKH solution + bromo blue).
     
  9. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Excellent. While you're at it you may also want to check the Nitrogen Newsletter, the Carbon Part 1, Carbon Part 2 and CO2 injection Newsletters as well.

    Theoretically, there really ought not to be a need to "clean" the water. Some inspiration can come by George Farmers post where he confirms that his PO4 id 5+ ppm and yet he has minimal algae. That's a significant data point (although it's always dangerous to compare two tanks directly).

    Another clue you mentioned is that you find yourself adjusting the CO2 injection rate in response to your drop checker. Could this be indicative of an unstable CO2 supply? I've never used DIY and I can't say with any certainty whether this is typical but I think quite possibly so. As stated many times by Tom Barr, CO2 instability is an invitation to algae regardless of the peak CO2 concentration levels. You may want to consider a pressurized system if you can afford it. After fiddling with the bubble rate for a few days you should not have to make constant adjustments to the flow. It shoul be low in the morning (assuming it is turned off at night-which, most agree it should be) It should peak to the green within an hour or less and should be stable in the green throughout the photoperiod.

    In any case, the consensus has been that unless you have unreasonably high Total Dissolved Solids in your tap water there should be no reason to fear its Phosphate or Nitrate content and unless you have a calibrated method of measurement you should always distrust the test kit readings. You should be able to dose the recommended concentrations of EI without reservation. Once this is established you should then look to stabilize CO2. The Phoszorb and Purigen should be considered adjuncts to the basic fertiization scheme and not as corrections to any weaknesses in that scheme.

    Hope this helps.

    Cheers,
     
  10. Maximumbob

    Maximumbob Member

    Messages:
    119
    Location:
    Cheshire, UK
    thanks again.. just need to sort out some money for the barr report wesite & CO2 system. I was all set to get it next month..... then came a whooping gas and electric bill. Maybe the following month then :(
     
  11. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    Some interesting topics have come up in this thread. EI is very dependant on good stable levels of CO2 otherwise plants will suffer and algae will prosper. Controlling CO2 levels using diy yeast systems is possible but hard to do. The drop checker needs to be green when lights come on till they go off.

    If everything is good in the tank PO4 levels actually drop pretty quick. If you do 50% water changes and your tap is 5ppm PO5 then you are actually adding 2.5ppm on tank volume which is fairly close to the first dosing amount anyway. Inorganic PO4 is still the way to go. I've never noticed high PO4 causing stunting or algae in my tank. algae.

    Tom keeps bashing on about CO2 is 90% plus of algae problems and he is correct. I can attribute a lot of my earlier problems with poor CO2.

    Subscribing to the Barr report is worth every penny IMO and is full of very informative information. I have definetely learnt loads from him.

    James
     

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